US8298946B2 - Method of selective coating of a composite surface production of microelectronic interconnections using said method and integrated circuits - Google Patents

Method of selective coating of a composite surface production of microelectronic interconnections using said method and integrated circuits Download PDF

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US8298946B2
US8298946B2 US10/599,214 US59921405A US8298946B2 US 8298946 B2 US8298946 B2 US 8298946B2 US 59921405 A US59921405 A US 59921405A US 8298946 B2 US8298946 B2 US 8298946B2
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metal
copper
process according
grafting
film
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US20090095507A1 (en
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Christophe Bureau
Sami Ameur
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Alchimer SA
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
    • C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
    • C23C18/1837—Multistep pretreatment
    • C23C18/1844—Multistep pretreatment with use of organic or inorganic compounds other than metals, first
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/1601—Process or apparatus
    • C23C18/1603—Process or apparatus coating on selected surface areas
    • C23C18/1607—Process or apparatus coating on selected surface areas by direct patterning
    • C23C18/1608—Process or apparatus coating on selected surface areas by direct patterning from pretreatment step, i.e. selective pre-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
    • C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
    • C23C18/1827—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment only one step pretreatment
    • C23C18/1834—Use of organic or inorganic compounds other than metals, e.g. activation, sensitisation with polymers
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1851—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material
    • C23C18/1872—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material by chemical pretreatment
    • C23C18/1875—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material by chemical pretreatment only one step pretreatment
    • C23C18/1882—Use of organic or inorganic compounds other than metals, e.g. activation, sensitisation with polymers
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1851—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material
    • C23C18/1872—Pretreatment of the material to be coated of surfaces of non-metallic or semiconducting in organic material by chemical pretreatment
    • C23C18/1886—Multistep pretreatment
    • C23C18/1893—Multistep pretreatment with use of organic or inorganic compounds other than metals, first
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
    • C23C18/28—Sensitising or activating
    • C23C18/30—Activating or accelerating or sensitising with palladium or other noble metal
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/76841—Barrier, adhesion or liner layers
    • H01L21/76843—Barrier, adhesion or liner layers formed in openings in a dielectric
    • H01L21/76849—Barrier, adhesion or liner layers formed in openings in a dielectric the layer being positioned on top of the main fill metal
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/76841—Barrier, adhesion or liner layers
    • H01L21/76871—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers
    • H01L21/76874—Layers specifically deposited to enhance or enable the nucleation of further layers, i.e. seed layers for electroless plating
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49117—Conductor or circuit manufacturing
    • Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
    • Y10T29/49155—Manufacturing circuit on or in base

Definitions

  • the present invention relates to a process for selectively coating certain areas of a composite surface with a conductive film, to a process for fabricating interconnects in microelectronics, and to processes and methods for fabricating integrated circuits, and more particularly to the formation of networks of metal interconnects, and also to processes and methods for fabricating Microsystems and connectors.
  • Integrated circuits are fabricated by forming discrete semiconductor devices on the surface of silicon wafers. A network of metallurgical interconnection is then established on these devices so to establish contacts between their active elements and to produce, between them, the wiring needed to obtain the desired circuit.
  • a system of interconnects consists of several levels. Each level is formed by metal lines and these lines are connected together by contacts called “interconnect holes” or “vias”.
  • the response time of an interconnect circuit is characterized by a constant RC, which corresponds roughly to the resistance R of the metal levels multiplied by their capacitive coupling represented by the constant C, mainly determined by the nature of the dielectric that separates the lines.
  • the metallization is carried out in three main steps:
  • the excess copper is removed by CMP.
  • the surface obtained is then in the form of a composite surface comprising alternating bands of copper and dielectric, each of the copper bands being bordered by a very fine semiconductor band, a vestige of the barrier layer installed in the trenches before filling with copper, and sliced off during the polishing.
  • these copper and dielectric bands are then conventionally encapsulated with a uniform layer of the SiC or SiCN type, covering the entire composite surface, and serving as a copper diffusion barrier.
  • these coatings are insulating, but they have a relatively high dielectric constant, which increases the capacitive coupling between copper lines.
  • one solution consists in using a barrier of the metal type, selectively deposited on the copper. This involves in fact depositing a copper diffusion barrier on the fourth side of the trenches, so as to completely enclose the copper lines in a “box”, from which they can no longer emerge.
  • this encapsulation barrier is highly adherent to the copper, the mobility of the copper at the copper/encapsulation barrier interface is greatly reduced and, consequently, the electrical current supported by the copper line, with no degradation, is higher and the resistance to electromigration increased.
  • the encapsulation barrier must be self-aligned with the subjacent copper so as to avoid leakage currents between neighbouring copper lines.
  • the approaches envisaged for this selective deposition are the selective chemical vapour deposition (CVD) of tungsten and the selective electroless plating with metal alloys.
  • CVD selective chemical vapour deposition
  • Metallic materials are therefore preferred because (i), in general, metals are considered to be more adherent to copper than dielectrics and (ii) the aforementioned selective techniques can be carried out for metals or alloys.
  • Electroless plating involves a reduction reaction in which a metal salt is reduced to metal, catalyzed on the surface of another metal.
  • the metal salt solutions allowing metals to be deposited without the intervention of an external current or voltage source are called metallization solutions or electroless solutions.
  • palladium activation barriers which comprise a step of forming palladium aggregates on the copper lines followed by a step of locally catalyzed growth of the metal barrier layer.
  • palladium activation barriers it is preferred to have palladium in the form of aggregates distributed over the copper lines, rather than in the form of a uniform layer, especially because:
  • palladium does have a number of advantages owing to the value of its standard redox potential, this is insufficient to allow real selectivity of the deposition of the palladium aggregates, especially on very fine structures (structures of 0.2 ⁇ m and below, that is to say etching sizes compatible with integrated circuit technological generations of 130 nm and below).
  • the inventors were therefore given the objective of providing a process meeting all these requirements, satisfying the aforementioned specifications and furthermore solving the many aforementioned problems of the prior art, especially for the fabrication of metal interconnects, integrated circuits or other microsystems.
  • the surfaces involved in the present invention have the particular feature of being composite surfaces, that is to say consisting of a tiling of areas differing at least by the work function of the material of which they are made.
  • the work function of a material is expressed in electron volts and corresponds to the energy to be delivered, in a vacuum, to a surface in order to extract an electron therefrom. More particularly, and as will be described hereinbelow, the present invention applies to composite surfaces, at least one subset of areas of which is electrically conductive.
  • the subject of the present invention is thus firstly a process for coating a composite material consisting of electrically conductive or semiconductive metal areas, particularly copper areas, and electrically non-conductive areas, the said process comprising at least one step of electroless growth of a metal layer plumb with the said electrically conductive or semiconductive metal areas, characterized in that the electrically non-conductive areas of the composite material are not formed from organic polymers and in that, prior to the said electroless growth step, the said process furthermore includes at least one first step of forming a nucleation layer by covalent or dative grafting of an organic or organometallic film on, and only on, the said electrically conductive or semiconductive metal areas, by bringing the said composite material into contact with organic or organometallic, difunctional precursors of the following formula (I): A-(X) n —B (I) in which:
  • the film thus formed has a thickness such that the free face of this film conforms to the local topology of the said composite surface on which it is placed.
  • the thickness of this film is between 1 and 100 nm, more preferentially between 1 and 10 nm and even more preferentially between 1 and 5 nm.
  • the layer serving for the selective growth of the metal layer therefore comprises an organic or organometallic film.
  • the film When the film is organometallic, it may be obtained either directly using precursors of the formula (I) which are themselves organometallic, that is to say in which B is a group having at least one ligand function that complexes metal ions, or via organic precursors, resulting in an organic film that is then treated with a solution of metal precursors that will be inserted onto or into the said film and allow “mordanting” of the grafted organic film.
  • This organometallic film therefore comprises, intermixed, an organic part and a metallic material, with or without chemical interactions or bonding between them, depending on the nature of the chemicals used.
  • the process furthermore includes a mordanting second step during which the organic or organometallic film formed on the electrically conductive or semiconductive metal areas is brought into contact with a mordanting solution comprising either at least one precursor of a metallic material or at least one precursor of a catalyst for its deposition, the said second step being carried out at the same time as or after the first step of forming the organic or organometallic film.
  • nucleation layer the nucleation or catalysis layer
  • Table I summarizes the various ways of carrying out the fabrication of the nucleation layer in accordance with the process according to the invention, depending on the nature of the grafted layer:
  • Step 1 Grafting Step 2: Step 3: Step 4: of the layer Mordanting Reduction of Electroless Method of organo- by metal the metal deposition implemen- organic metallic precursors precursors of the tation No. Nucleation layer, activation step metal layer I ⁇ — ⁇ — ⁇ II ⁇ — ⁇ ⁇ ⁇ III ⁇ — — — ⁇ IV — ⁇ — ⁇ ⁇ V — ⁇ — — ⁇ VI — ⁇ ⁇ — ⁇ VII — ⁇ ⁇ ⁇ ⁇ ⁇
  • nucleation layer may be formed in one or more steps. Whatever the number of steps needed for its fabrication, these steps will be called collectively by the name “grafting activation” steps when at least one of the steps includes a grafting reaction, that is to say a reaction involving the organic or organometallic precursors of formula (I) described above and resulting in the formation of an organometallic layer attached to the conductive or semiconductive areas of a composite surface by covalent or dative bonds.
  • the inventors have firstly found that the use of an organic film significantly improves the selectivity of the deposition of the nucleation layer and therefore of the upper metal layer, especially because the spontaneous surface chemistry and/or the chemical reactions initiated from the surface in order to obtain the organic film allows (allow) the geometrical topology of the composite surface to be maintained when they are accompanied by a chemical grafting reaction, that is to say when the adduct of the surface reaction with the precursors of these organic or organometallic films results in chemisorbed species on the conductive or semiconductive areas of the composite surface, that is to say species that form a dative or covalent bond therewith.
  • the inventors have observed that the selectivity obtained with this type of reaction is greater than that obtained in a direct manner using the known techniques of the prior art, that is to say by electroless deposition.
  • the non-polymeric nature of the electrically non-conductive areas of the composite material used according to the process of the invention allows the selective attachment of the organic film only plumb with the electrically conductive or semiconductive areas, insofar as the compounds of formula (I) as defined above cannot be attached thereto via covalent or dative bonds.
  • the inventors have also observed the property of many organic materials constituting such films of being able to accommodate and/or support one or more precursors of metallic materials and to convert these precursors into the said metallic materials within these organic films or on their surface, especially when these films possess reactive functional groups capable of allowing the formation of dative or covalent bonds with precursors of metallic materials or with the metallic materials themselves.
  • the process according to the invention thanks to the presence of organic film plumb with the electrically conductive or semiconductive areas, makes it possible to considerably reduce the concentration of the metal ion, especially palladium ion, solutions used to carry out the mordanting step.
  • the presence of this organic film makes it possible in particular to employ metal ion solutions having a concentration of less than 10 ⁇ 4 M, that is to say solutions that are much less concentrated than the solutions normally used in the processes of the prior art.
  • the reactive function of the group A of the difunctional, organic or organometallic, precursors of formula (I) above is chosen from functions carrying lone pairs, such as the following functions: amine, pyridine, thiol, ester, carboxylic acid, hydroxamic acid, thiourea, nitrile, salicylic, amino acid and triazine; the radicals obtained from cleavable functions, such as disulphide, diazonium (—N 2 + ), sulphonium, iodonium, ammonium, alkyl iodide or aryl iodide functions; carbocations; carbanions (and especially those obtained via alkynes, organocuprates and organomagnesium, organozinc or organocadmium compounds).
  • functions carrying lone pairs such as the following functions: amine, pyridine, thiol, ester, carboxylic acid, hydroxamic acid, thiourea, nitrile, salicylic, amino acid
  • X is a spacer arm linked covalently to the groups A and B, and able to contribute to the stability of the molecule.
  • X is preferably chosen from rings or from conjugated or unconjugated combinations of aromatic rings; saturated or unsaturated, branched or linear, aliphatic chains; and assemblies of these two types of functions, optionally substituted with electron-withdrawing or electron-donating groups in order to contribute to the stability of the entire molecule.
  • spacer arms X As examples of spacer arms X, mention may especially be made of linear or branched alkane chains (—(CH 2 ) m —, with 1 ⁇ m ⁇ 25) such as, for example, methylene (—CH 2 —) groups; the phenylene group (—C 6 H 4 —); phenylene groups substituted with electron-withdrawing groups, such as nitro, cyano or hydroxyl groups, etc., or electron-donating groups such as alkyl groups, preferably having from 1 to 4 carbon atoms such as, for example, the methyl group; groups carrying several fused aromatic rings, such as naphthylene or anthrylene groups, etc., which are themselves optionally substituted with one or more electron-donating or electron-withdrawing groups; and also structures consisting of combinations of these groups.
  • linear or branched alkane chains such as, for example, methylene (—CH 2 —) groups; the phenylene group (—C 6 H 4 —); phenylene groups
  • spacer arms X of formula —(CH 2 ) m , in which m is an integer not exceeding 10, are particularly preferred according to the invention.
  • ligand functions defined above in respect of the part B of the difunctional, organic or organometallic, precursors of formula (I) mention may in particular be made of amines, amides, pyridines, nitrites, amino acids, triazines, bipyridines, terpyridines, quinolines, orthophenanthroline compounds, ethers, carbonyls, carboxyls and carboxylates, esters, hydroxamic acids, salicylic acids, phosphines, phosphine oxides, thiols, thioethers, disulphides, ureas, thioureas, crown ethers, aza-crown compounds, thio-crown compounds, cryptands, sepulcrates, podands, porphyrins, calixarenes, naphthols, isonaphthols, siderophores, antibiotics, ethylene glycol and cyclodextrins; substituted and/or
  • the function X may be “fused” into one and the same group with the groups A or B: this is the case for example when considering a pyridine carrying a group that can be grafted onto a metal, the latter group being, for example, in the para position of the nitrogen of the pyridine.
  • the reactive function is this graftable group, and the pyridine ring takes the place both of X and of the ligand function, the X being the carbon part of the pyridine ring and the ligand function being the nitrogen of the pyridine ring, which is known to have complexing functions with respect to metals.
  • Pyrimidines for example also fall within this category.
  • aryldiazonium salts mention may most particularly be made of 4-ethylammonium phenyldiazonium tetrafluoroborate, 4-(2-aminoethyl)benzenediazonium ditetrafluoroborate, 4-cyanobenzenediazonium tetra-fluoroborate, 4-carboxy-3-hydroxybenzenediazonium tetrafluoroborate, 3-carboxy-4-nitrobenzenediazonium tetrafluoroborate, 4-carboxybenzenediazonium and 4-thioethanolphenyldiazonium tetrafluoroborate.
  • the compounds of formulae (I-1) to (I-14) below are examples of grafting adducts obtained, for example, from aryldiazonium salts, the cleavage of which results in the formation of carbon/metal covalent bonds:
  • the structures (I-1) to (I-14) above have been shown once the grafting onto conductive area (M) of a composite material has been carried out and, optionally, once the metal mordanting has been carried out.
  • the palladium or copper ions being shown merely by way of illustration: it is observed in fact that the ligand functions that are carried by the molecules thus grafted are rarely selective of a given ion, but in general have an affinity for many metal ions, and in particular for all transition metal ions.
  • the present invention makes it possible to significantly improve the coating processes that include a palladium activation step, but also permits an immediate transposition to activations other than by palladium (as shown in Table I above, for methods of implementation I, II, VI and VII, the mordanting may be carried out after the grafting, but with metal precursors other than palladium precursors, and especially with cobalt or nickel precursors, or precursors of any other element present thereafter in the electroless solution), or even without palladium (the mordanting is not carried out, and the electroless solution is used directly on the grafted layer, as is the case in the method of implementation III of Table I above).
  • the molecules of formula (I) described above may be deposited in various ways on the conductive areas of composite surfaces, depending in particular on the nature of the functional group A: in most cases, it is observed that the aforementioned groups can react spontaneously and preferentially on the conductive or semiconductive areas of the composite surfaces, resulting in the formation of grafted organic layers, to the exclusion of the insulating areas, in which case simple contacting of the composite surface with a solution containing the molecules of formula (I) (for example by dipping, spin coating or spraying) may be suitable. There is then chemical grafting of the organic film onto the conductive or semiconductive areas of the composite surface.
  • the complexation, the reduction and the electroless growth take place in a single step, thereby making it possible to restrict the number of steps substantially. Thanks to the activation by grafting, the abovementioned advantages, and especially the insensitivity of the steps prior to the activation, the high degree of selectivity offered by the grafting, and the additional degree of freedom offered by the grafting for the growth of the electroless plating layer, apply;
  • the present invention addresses the drawbacks of the processes known from the prior art, by improving the selectivity of the metal platings thanks to an activation step involving a chemical grafting reaction.
  • the surfaces involved in the present invention are as many as the various possible applications of the present invention. These may be conductive or semiconductive surfaces of three-dimensional objects, or completely or partly semiconductive surfaces.
  • the term “three-dimensional surface” is understood to mean a surface whose topological irregularities are dimensionally not insignificant relative to the thickness of the coating that it is desired to obtain. It may for example be the surfaces of substrates used for the fabrication of Microsystems or of integrated circuits, for example surfaces of silicon wafers and other materials known to those skilled in the art in the technical field in question.
  • the substrate may for example be an inter-level layer for the fabrication of an integrated circuit, and especially the surface obtained by chemical-mechanical polishing (CMP) after a step of depositing a thick copper electroplating layer and of filling the trenches and/or vias in the production of copper interconnects in the damascene or dual damascene process.
  • CMP chemical-mechanical polishing
  • the composition material comprises surfaces that are almost planar and consisting of an alternation of copper tracks of width L separated by dielectric tracks. The narrowest widths are those of the first metal level (level M 1 ).
  • the roadmap establishing fabrication processes in microelectronics sets the width L at about 120 nm in 90 nm technology, 85 nm in 65 nm technology, 50 nm in 45 nm technology and 40 nm in 32 nm technology. According to the invention, this width L is therefore preferentially between about 150 and 30 nm. It is therefore apparent that the present invention will be all the more relevant to the technological evolution during the decades to come, given the need to be able to obtain high selectivity of the electroless metal plating in order to cap increasingly narrow copper lines separated by increasingly narrow dielectric tracks.
  • the process of the present invention therefore solves the many problems mentioned above of the prior art that use processes which, on these scales, result in coatings extending above the dielectric tracks and producing an undesirable short circuit of the copper tracks.
  • the process of the invention also offers the possibility of metal interconnect dimensions hitherto never achieved.
  • the precursors of the metallic material that serve for the nucleation layer and are used in the mordanting solution during the second step of the process according to the present invention are preferably chosen from metal ions, among which mention may be made of copper, zinc, gold, tin, titanium, vanadium, chromium, iron, cobalt, lithium, sodium, aluminium, magnesium, potassium, rubidium, caesium, strontium, yttrium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, indium, lutecium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, mercury, thallium, lead and bismuth ions, ions of the lanthanides and of the actinides, and mixtures thereof.
  • metal ions among which mention may be made of copper, zinc, gold, tin, titanium, vanadium, chromium, iron, co
  • metal precursor may advantageously consist of copper, palladium or platinum ions.
  • the metal ion concentration within the mordanting solution used to produce this nucleation layer preferentially does not exceed 10 ⁇ 4 M and even more preferably does not exceed 10 ⁇ 5 M.
  • the organometallic precursor may contain not metal ions, but directly metal particles or aggregates.
  • Such structures exist, and are stable when the metal particles or aggregates are encapsulated in a protective “gangue” chosen from the group consisting of polymer micelles or nanospheres, fullerenes, carbon nanotubes and cyclodextrins.
  • the process according to the invention then preferably includes a step of releasing the particles or aggregates from their gangue, in addition to the grafting step.
  • attachment of the metal precursor onto, or insertion into, the grafted organic film may be carried out by means of any technique which is suitable, taking into account the chemical nature of the film and of the precursor of the metallic material.
  • the techniques that can be used within the context of the present invention for this step are therefore numerous—they go from simply bringing the precursor of the metallic material into contact with the organic film placed on the surface of the composite material, for example by dipping the organic film grafted onto the conductive areas of the composite into a suitable solution of the said precursor, for example of the type of those used in the prior art for electroless plating and such as described for example in U.S. Pat. No. 5,695,810, to more sophisticated techniques such as spin coating or spraying onto the surface of the said composite material.
  • One or other of the aforementioned methods of implementation thus allows the formation of an ultrathin film of precursor of the metallic material, which is adherent, selective and, in particular, conformal. This is because, unlike all the processes of the prior art, the process according to the invention makes it possible to forcibly localize the precursor of the metallic material on the conductive or semiconductive areas of the surface of the composite material, within the organic film conforming laterally to the topology of the said surface.
  • the mordanting solution used during the second step of the process according to the invention is a solution that allows the precursor of the metallic material to be conveyed right to the ligand functions of the groups B of the compounds of formula (I), thus allowing them to be complexed on and/or within the grafted organic film.
  • This is therefore a solution that allows sufficient dissolution or dispersion of the metal precursor for carrying out the present invention. This is because, in the case of insoluble salts of the precursor of the metallic material, this solution must preferably be able to disperse the precursor of the metallic material sufficiently to be able to allow this precursor to be inserted into the organic film.
  • the mordanting solution will therefore be chosen according to many criteria, among which the following may be mentioned: a surface criterion, for example in order to avoid chemical interactions such as the oxidation of the surface during implementation of the process; an organic film criterion, so that this solution does not remove film from the surface on which it has been deposited; a metallic material precursor criterion, which must allow it to be dissolved, but also allow it to be transformed into a metallic material; and a metallic material criterion, which must allow its formation within the organic film, and especially allow its deposition process to be carried out, for example its autocatalytic deposition.
  • a surface criterion for example in order to avoid chemical interactions such as the oxidation of the surface during implementation of the process
  • an organic film criterion so that this solution does not remove film from the surface on which it has been deposited
  • a metallic material precursor criterion which must allow it to be dissolved, but also allow it to be transformed into a metallic material
  • the solvent of the mordanting solutions is preferably chosen from solvents that have a good solubilizing power for ions, and therefore a satisfactory dissociating power, such as water; alcohols, such as ethanol, methanol or isopropanol; dimethylformamide (DMF); dimethylsulphoxide (DMSO); or else acetonitrile.
  • the subject of the invention is also the composite material comprising at least one surface consisting of an alternation of electrically conductive or semiconductive areas and electrically non-conductive areas, which can be obtained by implementing the process according to the present invention and as described above, characterized in that the electrically non-conductive areas of the composite material are not formed from organic polymers and in that the electrically conductive or semiconductive areas are covered with a nucleation layer grafted covalently or datively and consisting of difunctional, organic or organometallic compounds of the following formula (I) A-(X) n —B (I) in which:
  • A, X and B are as defined above.
  • the implementation of the process according to the invention is particularly advantageous in the field of microelectronics.
  • the subject of the present invention is also a process for fabricating interconnects in microelectronics, electronic Microsystems or integrated circuits, characterized in that the said process includes at least one step of grafting a film of difunctional precursors of formula (I) using the coating process as described above, the said interconnects being made of a metallic material.
  • the process for fabricating metal interconnects according to the present invention is characterized in that it comprises, in the following order, the steps consisting in:
  • the subject of the present invention is the use of such a process for the fabrication of interconnect elements in microelectronics, of electronic Microsystems or of integrated circuits, and also the use of the interconnect elements in microelectronics, the electronic Microsystems and the integrated circuits that are obtained using such a process.
  • the coating process according to the invention may also be applied to the selective metallization of the source and drain of MOS transistors.
  • the invention also includes other arrangements that will become apparent from the following description, which refers to examples in which the copper lines of integrated circuits are activated after CMP by the grafting of a cysteamine film, a 4-ethyl(ammonium tetrafluoroborate)-diazonium tetrafluoroborate film or an ethylenediamine film, to an example of the grafting of various diazonium salts onto metals, to an example for the production of self-aligned barriers using a process comprising an activation step carried out by grafting according to the process of the invention, and to an example of the regioselective grafting of a palladium aggregate via a grafting step according to the process of the invention, and also to the appended FIGS. 1 to 18 in which:
  • FIG. 1 shows a perspective view, obtained by scanning electron microscopy at a magnification of 50 000, of the surface of a 5 ⁇ 1 cm 2 coupon obtained by cleaving an etched silicon wafer and comprising an alternation of copper and dielectric lines after CMP but before cleaning;
  • FIG. 2 shows a view via the edge of the coupon shown in FIG. 1 , at a magnification of 100 000;
  • FIG. 3 shows a perspective view at a magnification of 50 000 of the coupon of FIG. 1 , but after cleaning with a cleaning solution;
  • FIG. 4 shows an edge view at a magnification of 100 000 of the coupon of FIG. 2 , but after cleaning with a cleaning solution;
  • FIG. 5 shows a perspective view at a magnification of 50 000 of the coupon of FIG. 3 , after activation of the surface by grafting of a cysteamine film and mordanting with a palladium solution;
  • FIG. 6 shows an edge view at a magnification of 100 000 of the coupon of FIG. 4 , after activation of the surface by grafting of a cysteamine film and mordanting with a palladium solution;
  • FIG. 7 shows an edge view at a magnification of 80 000 of the coupon of FIG. 3 after treatment with a solution allowing the deposition of a metal layer using an electroless process
  • FIG. 8 shows the infrared reflection absorption spectra (IRRAS) of silicon coupons (peak intensity as a function of the wavenumber in cm ⁇ 1 ) and illustrates the variation in the grafting of a diazoanhydride film after 2, 10, 30 and 60 minutes of immersion in a diazoanhydride grafting solution.
  • the curve at the top corresponds to an immersion time of 2 minutes, and then the others that follow, downward and in this order, correspond to immersion times of 10, 30 and 60 minutes;
  • FIG. 9 shows the IRRAS spectra for two diazoanhydride layers obtained by immersing, for 30 minutes at room temperature, two semi-polished copper surfaces in a grafting solution containing 2 ⁇ 10 ⁇ 3 mol/l of diazoanhydride in acetonitrile, before and after immersion in an ultrasonic bath in acetonitrile for 1 hour (bottom curve: before immersion; top curve: after immersion);
  • FIG. 10 shows the “comb/coil” features of an integrated circuit comprising an alternation of copper and dielectric lines
  • FIG. 11 shows the leakage current expressed in amps as a function of the etching dimension, that is to say the comb/coil distance expressed in ⁇ m, on a circuit according to that of FIG. 13 using a conventional process not involving a step of grafting an organic or organometallic film;
  • FIG. 12 shows the leakage current expressed in amps as a function of the etching dimension, that is to say the comb-coil distance expressed in ⁇ m on a circuit according to that of FIG. 13 using a process according to the present invention, that is to say one that includes a step of grafting a cysteamine film;
  • FIG. 13 is a perspective SEM view at a magnification of 50 000 of a silicon coupon having 0.16 ⁇ m etched copper features after treatment according to a conventional process of the prior art, one that does not include a step of grafting a compound of formula (I);
  • FIG. 14 is a perspective SEM view at a magnification of 50 000 of a silicon coupon that includes 0.16 ⁇ m etched copper features after treatment using the process according to the invention, that is to say one that includes a step of grafting a cysteamine film, the said process also including, after CMP, a cleaning step using a citric acid solution;
  • FIG. 15 is a perspective SEM view at a magnification of 50 000 of a silicon coupon comprising 0.16 ⁇ m etched copper features after a treatment using the process according to the invention, that is to say one that includes a step of grafting a cysteamine film, the said process also not including any cleaning step after CMP;
  • FIG. 16 is a perspective SEM view at a magnification of 50 000 of a silicon coupon comprising an alternation of copper and dielectric lines and treated using the process according to the invention, that is to say that includes a step of grafting a cysteamine film with a solution containing 56.8 g of aminoethanethiol and 98% HCl (cysteamine) in 100 ml of ethanol;
  • FIG. 17 is a perspective SEM view at a magnification of 50 000 of a silicon coupon comprising an alternation of copper and dielectric lines and treated using the process according to the invention, that is to say one that includes a step of grafting a cysteamine film with a solution containing 113.6 g of aminoethanethiol and 98% HCl (cysteamine) in 100 ml of ethanol; and
  • FIG. 18 is a perspective SEM view at a magnification of 50 000 of a silicon coupon comprising an alternation of copper and dielectric lines and treated using the process according to the invention, that is to say one that includes a step of grafting a cysteamine film with a solution containing 227.2 g of aminoethanethiol and 98% HCl (cysteamine) in 100 ml of ethanol.
  • This example is used to demonstrate the selective formation of catalytic palladium aggregates on 200 nm wide copper lines by the prior grafting of an organic layer using cysteamine as compound of formula (I).
  • the composite surfaces used were 5 ⁇ 1 cm 2 coupons obtained by cleaving etched integrated circuits (silicon wafers), after deposition of a TiN barrier, formation of a copper nucleation layer by physical vapour deposition, electrochemical filling with copper by electroplating and then chemical-mechanical polishing until the dielectric projections had been clipped off, so as to produce surfaces made from an alternation of copper tracks and dielectric (SiO 2 ) tracks.
  • the surface was cleaned using a cleaning solution (S clean ) after which the surface was treated with the grafting solution (S graft ) and then with the catalyst solution (S cata ) containing palladium ions as metal precursors.
  • the surfaces thus treated were cleaved perpendicular to the direction of the trenches, and then examined via the edge by scanning electron microscopy (SEM).
  • FIGS. 1 and 2 appended hereto show views, in perspective ( ⁇ 50 000 magnification) and via the edge ( ⁇ 100 000 magnification), respectively, of the surface before cleaning, i.e. after the CMP, revealing a number of impurities.
  • FIGS. 3 and 4 show the same surfaces at the same magnifications after cleaning (solution S clean ) using the protocols indicated above.
  • FIGS. 5 and 6 show (at the same magnifications) the result obtained after activation by grafting (with S graft ) then mordanting with the palladium solution (S cata ).
  • FIG. 7 ( ⁇ 80 000 magnification) shows an edge view of a surface as obtained in FIGS. 5 and 6 after treatment with a solution of metal ions for a metal plating using an electroless process.
  • This example is used to demonstrate the selective formation of catalytic palladium aggregates on 200 nm wide copper lines by the prior grafting of an organic layer using a diazonium salt (DZ-NH 3 + ).
  • the specimens and cleaning solution (S clean ) and catalytic solution (S cata ) were identical to those described above in Example 1.
  • the grafting solution (S graft ) was composed of 64.6 mg of DZ-NH 3 + in 100 ml of acetonitrile.
  • the copper/SiO 2 composite surfaces were cleaned using the same protocol as described above in Example 1, then immersed for 15 minutes in the grafting solution, then rinsed with a 0.1 mol/l aqueous sodium hydroxide solution and then mordanted by the catalytic solution as in Example 1.
  • This example is used to demonstrate the selective formation of catalytic palladium aggregates on 200 nm wide copper lines by the prior grafting of an organic layer using EDA.
  • This example is used to demonstrate the spontaneous grafting of various diazonium salts onto copper surfaces.
  • the diazonium salts used in this example were the following:
  • the specimens used were 5 ⁇ 1 cm 2 silicon coupons obtained by cleaving from a plane silicon wafer (i.e. not having etched features) covered with an approximately 500 nm SiO 2 layer, a 15 nm TiN layer, an approximately 50 nm copper nucleation layer formed by physical vapour deposition and then a thick (approximately 1.5 micron) copper plating obtained by electroplating.
  • the wafer was then polished by CMP polishing over half the thickness of thick copper (called a “semi-polished” wafer) so as to deliver a plane, structureless copper surface having the same composition as the copper tracks after the CMP treatment.
  • the coupons thus prepared were immersed for 30 minutes in the S graft 01 to S graft 15 solutions presented above. After 30 minutes, the formation of grafted organic films was observed, these being perfectly resistant to the rinsing operations performed.
  • the surfaces thus treated were analyzed by infrared reflection absorption spectroscopy (IRRAS) and clearly show the formation of an organic film exhibiting absorption bands characteristic of the functional groups carried by the precursor diazonium salts, as shown in Table V below:
  • FIG. 8 shows the variation of the grafting as a function of the immersion time of the coupons in the grafting solution, showing the IRRAS spectrum for the grafted diazo layer after various immersion times of 2, 10, 30 and 60 minutes.
  • the curve at the top corresponds to an immersion time of 2 minutes and then those that follow downwards, and in this order, correspond to immersion times of 10, 30 and 60 minutes.
  • the characteristic absorption bands of the diazo film are more intense as the time in contact with the grafting solution increases, which may be attributed to a densification of the film, since it was observed elsewhere that, at the same time, its thickness changed little.
  • FIG. 9 shows the IRRAS spectra for two diazoanhydride layers obtained by immersion for 30 minutes at room temperature of two semi-polished copper surfaces in a grafting solution containing 2 ⁇ 10 ⁇ 3 mol/l of diazoanhydride in acetonitrile, one of which was then treated in an ultrasonic bath in acetonitrile for 1 hour (top curve).
  • This example is used to illustrate the improvements in performance provided by the grafting according to the process of the invention in the activation of composite surfaces during the fabrication of self-aligned barriers.
  • the substrates used were 5 ⁇ 1 cm 2 coupons obtained by cleaving etched silicon wafers comprising, as in the previous examples, an SiO 2 layer (the dielectric), a TiN layer, a copper nucleation layer formed by physical vapour deposition, and a thick copper layer obtained by electroplating, and then treated by a CMP step until the dielectric lines were exposed.
  • the starting surfaces were therefore composite surfaces consisting of alternations of copper and dielectric lines.
  • the tracks shown in FIG. 10 are copper tracks on which it was desired to produce a highly selective plating of a metal barrier.
  • the “leakage current” measurement was performed, by measuring the electrical current flowing between the comb and the coil, when they were subjected to a potential difference. If the plating is ultraselective, there is no short circuit between the combs and the coil, and the measured leakage current is identical, or close, to that measured at the start between the bare copper tracks. At the slightest short circuit, a high “leakage current” is detected, which shows that the plating on the copper lines has not been selective. This test is even more drastic as a single short circuit point along the coil is sufficient to generate high leakage currents. It is therefore necessary for the plating process to be robust in order to obtain relevant results.
  • the structures were such that the coils had a total length of 12 and 70 mm.
  • Each coupon specimen carried several structures in which the spacing between the combs and the coil was different each time. This made it possible to test, on one and the same specimen, decreasing sizes of structure and to demonstrate the benefits of the capping technology for the finest structures.
  • FIG. 11 shows the leakage currents obtained for specimens treated using the conventional processes of the prior art, and therefore not forming part of the invention, namely a copper/SiO 2 composite starting substrate and the Cu/SiO 2 composite substrate after cleaning, palladium activation and electroless plating. It shows that the leakage currents obtained are higher on the finer structures (in particular the 0.2 ⁇ m structures).
  • FIG. 12 shows the results obtained in the process of the invention when a grafting step is firstly inserted in order to enhance the palladium activation.
  • the following sequence was then used overall for the activation: cleaning of the support; grafting of the cysteamine using the protocol described above in Example 1; palladium activation+electroless plating. It may be seen that the leakage currents obtained are substantially lower than those obtained above with the conventional process of the prior art, which does not include a step of grafting a difunctional precursor of formula (I). It is important to note that the same palladium activation protocol was used in both cases.
  • FIGS. 13 , 14 and 15 are SEM photomicrographs at magnification of 50 000, which show the morphology of the platings obtained on 0.16 ⁇ m etched features, respectively with the conventional protocol not forming part of the invention (no grafting), according to the invention, i.e. including a step of grafting cysteamine as difunctional precursor of formula (I), and according to the protocol defined in Example 1 above, with or without cleaning prior to the grafting step.
  • the selectivity is, of course, superior with the process according to the invention, that is to say one that includes a grafting step (compare FIGS. 13 and 14 ), and that identical morphologies are obtained with or without cleaning prior to the grafting step (compare FIGS. 14 and 15 ).
  • the line resistances are not detectably modified by the grafting step (results not shown), which means, as a result of the grafting activation, a process which is promising from the industrial standpoint.
  • This example is used to illustrate the control that the grafting allows in controlling the densities and sizes of the aggregates obtained during a palladium activation step.
  • Example 2 Carried out on Cu/SiO 2 composite surfaces identical to those used above in Example 1 was a sequence comprising: a cleaning step; a cysteamine grafting step; and a palladium mordanting step.
  • the solutions and protocols used were the same as those described above in Example 1. Only the concentration of the cysteamine in the grafting solution was adjusted. Three grafting solutions were produced:
  • the mordanting was carried out with a palladium solution identical to that of Example 1.
  • the same mordanting solution and the same mordanting protocol were used in all the plates of the present example.
  • FIG. 16 shows an SEM photo at ⁇ 50 000 magnification of the results obtained with a grafting step using the grafting solution S graft F.
  • FIG. 17 shows the results obtained with the grafting solution S graft M and FIG. 18 with the grafting solution S graft H.
  • the concentration of grafting precursor in the organic bath allows the density and the size of the aggregates to be adjusted, the solution S graft H in fact delivering a greater amount of palladium plating than the solution S graft M, which itself gives a more dense plating than the solution S graft F.
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IL178218A0 (en) 2006-12-31
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TWI384524B (zh) 2013-02-01
FR2868085B1 (fr) 2006-07-14
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US20090095507A1 (en) 2009-04-16
TW200535972A (en) 2005-11-01
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IL178218A (en) 2013-10-31
WO2005098087A3 (fr) 2006-05-18

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